Learn Hardcore Russian: Я всегда записываю логин и пароль в блокнот, чтобы потом не искать их. - I always write down the login and password in a notebook so I don't have to look for them later.

Я всегда записываю… = I always write down… (general habit)
Я запишу логин и пароль… = I will write down the login and password (this time / in the future).
Я записал(а) логин и пароль… = I wrote down the login and password (on one specific occasion).

Because of всегда (always), the sentence is about a regular habit, so the imperfective present записываю is the natural choice.

What is the function of всегда here, and can it go in a different place in the sentence?

Всегда means always and marks the action as a regular, repeated habit.

The neutral position is right after the subject:

Я всегда записываю… – I always write down…

Other possible positions and nuances:

Всегда я записываю логин и пароль в блокнот… – sounds more emphatic or stylistic, like “It’s always that I write down…”
Я записываю всегда логин и пароль в блокнот… – possible, but a bit less natural; emphasis shifts slightly to the fact that it’s this action that is always done.

For everyday speech, Я всегда записываю… is the standard word order.

Why do логин and пароль look like they are in the nominative case when they are objects?

They are direct objects, so they are in the accusative case. But both are masculine inanimate nouns, and for that group the accusative form equals the nominative form.

Nominative: логин, пароль
Accusative (inanimate): логин, пароль

So even though they look like nominative, grammatically they are accusative because they answer what? after the verb:

записываю (что?) логин и пароль

Why is it в блокнот and not в блокноте or на блокнот?

The choice depends on both the preposition and the case:

В блокнот (accusative)
- literally: into the notebook
- implies direction / putting something into the notebook (writing into it).
- This is correct here because you’re transferring information into the notebook.
В блокноте (prepositional)
- in the notebook (location, “inside”)
- would be used for something like:
  - Логин и пароль у меня записаны в блокноте. – My login and password are written in the notebook.
На блокнот
- literally onto the notebook (onto the cover, surface)
- would sound like physically writing on top of the notebook, not inside; usually wrong here.

So в блокнот is correct because you are writing something into the notebook.

What exactly does чтобы do in чтобы потом не искать их?

Чтобы introduces a purpose clause: it answers the question “for what purpose?” or “why?”.

…записываю логин и пароль в блокнот, чтобы потом не искать их.
= I write them down in a notebook *so that I don’t have to look for them later.*

The general pattern:

делать что-то, чтобы…
- infinitive or verb
  to do something in order to…

Here, чтобы + не искать expresses the goal of the action: you write them down in order not to search for them later.

Why is it не искать (infinitive) and not не искал(а) or some other tense after чтобы?

With чтобы, there are two common patterns:

Чтобы
- finite verb (often with бы):
- Я записываю логин и пароль, чтобы потом не пришлось их искать.
  …so that I wouldn’t have to look for them later.
Чтобы
- infinitive (as in this sentence):
- Я записываю логин и пароль, чтобы потом не искать их.
  …in order not to look for them later.

The infinitive after чтобы is widely used in everyday speech when:

the subject is the same for both parts (I write them down and I won’t search for them), and
the style is neutral / colloquial rather than very formal.

So чтобы не искать is natural and idiomatic here.

Why is the verb искать (to search) imperfective here and not найти (to find)?

Искать (imperfective) focuses on the process of searching, whereas найти (perfective) focuses on the result of finding.

не искать их – not have to search for them (avoid the searching process)
не искать их, а сразу найти – not search for them, but find them immediately

The idea in this sentence is: I write them down so I won’t need to go through the *searching process later.
So the *imperfective искать is exactly what you want.

What does их refer to, and why is it их and not another pronoun?

Их is the genitive/accusative plural form of the third-person pronoun они (they).

In this context:

логин и пароль = two items → plural “they”
When they become the object of искать, we use их:
- искать кого? что? – их (look for them)

So их refers back to логин и пароль together.
You cannot use его (him/it) or её (her/it) here, because there are two objects, not one.

Can the word order be changed, for example to логин и пароль я всегда записываю в блокнот?

Yes, Russian word order is relatively flexible, and those changes mainly affect emphasis:

Я всегда записываю логин и пароль в блокнот…
– neutral, standard focus on the action/habit.
Логин и пароль я всегда записываю в блокнот…
– emphasizes логин и пароль:
As for the login and password, I always write them in a notebook…
(Maybe in contrast to other data that you treat differently.)
Я логин и пароль всегда записываю в блокнот…
– emphasizes that it’s always that you do this with login and password.

All are grammatically correct; the original is the most neutral and common.

What is the difference between потом and позже here? Could we say чтобы позже не искать их?

Both потом and позже can often mean later, but there is a nuance:

Потом – “then, afterwards, later on” in a more sequence-like, narrative sense; very common in speech.
Позже – more like “later” in the sense of at a later time, sometimes a bit more neutral/formal.

In this sentence:

чтобы потом не искать их – absolutely natural and idiomatic.
чтобы позже не искать их – grammatically fine, but sounds slightly less natural; потом is preferred in this everyday context.

So yes, позже is possible, but потом feels more colloquial and typical here.

Is логин a normal Russian word? What gender is it and how does it decline?

Yes, логин is a fully integrated loanword in modern Russian IT/Internet vocabulary.

Gender: masculine
Declension: regular masculine noun

Singular:

Nominative: логин
Genitive: логина
Dative: логину
Accusative (inanimate): логин
Instrumental: логином
Prepositional: о логине

In many contexts, people also use:

имя пользователя – username
учётная запись – account (slightly different meaning, broader)

But in this sentence логин is the usual everyday term.

Could we use пишу instead of записываю? What is the difference?

You could say:

Я всегда пишу логин и пароль в блокнот…

but there is a nuance:

писать – to write in general (the physical act).
записывать – to write down / record / note something for future use, with a sense of making a note, registering.

Because the purpose is exactly to make a note so you don’t have to search later, записываю fits better.
Пишу would be understood, but it sounds less precise about the idea of recording for later reference.

Does блокнот have to be a physical paper notebook, or can it be digital (like a notes app)?

Literally, блокнот is a (paper) notepad / notebook, but in modern usage it can also refer to a digital notebook or note-taking app, depending on context.

Physical: a small paper notebook where you jot things down.
Digital (by context/slang): блокнот в телефоне, блокнот в компьютере etc.

If you want to be explicit about digital notes, you might say:

…в заметки на телефоне – in the notes on my phone
…в приложение для заметок – in a note-taking app

But in casual speech, people can still say в блокнот, and the context will clarify whether it’s physical or digital.