In de browser kun je een nieuw tabblad openen als je rechtsboven klikt.

Because Dutch main clauses usually follow the verb-second rule.

Here, In de browser is placed first, so the finite verb has to come next:

• In de browser kun je ...

If you started with the subject, you would normally say:

• Je kunt in de browser ...

Both mean the same thing here. The difference is mainly word order.

Dutch often puts a time, place, or other extra piece of information at the beginning of the sentence for emphasis or context.

So:

• In de browser kun je ...

means something like In the browser, you can ...

It sets the scene first. This is very common in Dutch.

Because tabblad is a het-word: het tabblad.

With an indefinite singular neuter noun after een, the adjective usually has no -e ending:

• een nieuw tabblad

Compare:

• het nieuwe tabblad
• een nieuwe pagina

So the rule is:

• een + het-word (singular) → often no -e
• de-word or definite noun → usually -e

Because kunnen is a modal verb.

In Dutch, when you use a modal verb such as kunnen, willen, moeten, mogen, or zullen, the second verb usually stays in the infinitive and goes to the end of the clause:

• je kunt een nieuw tabblad openen
• ik wil dat doen
• we moeten gaan

So here:

• kun je ... openen

is the normal pattern.

Here als can feel like if or when, depending on context.

In instructions like this, it often means something like:

• if you click in the top right
• or when you click in the top right

Dutch als is often used where English might choose either if or when.

It also introduces a subordinate clause, which is why the verb goes to the end:

• als je rechtsboven klikt

Rechtsboven means at the top right or in the upper-right corner.

Dutch often combines direction words into one adverb:

• rechts = right
• boven = above / up

Together:

• rechtsboven = top right / upper right

This is very common, especially for screen or page positions.

Because there are two clauses, and each clause needs its own subject.

Main clause:

• kun je een nieuw tabblad openen

Subordinate clause:

• als je rechtsboven klikt

Both subjects are je, and they refer to the same person, but grammatically each clause still needs one.

Because rechtsboven gives a location, not a specific object.

Dutch often uses:

• op iets klikken = click on something

For example:

• Klik op de knop.

But when you mean clicking somewhere on the screen, Dutch can simply say:

• rechtsboven klikken

So this means click in the top right area.

If you named an object, op would be more likely:

• Klik op het icoon rechtsboven.

Yes. In standard Dutch, browser is normally a de-word:

• de browser

So you say:

• In de browser ...

Unfortunately, whether a noun is a de-word or het-word often has to be learned word by word. But for this noun, de browser is the normal form.