I think I need a bit more info . Is this a working space or a home office ? How much larger desk do you need Seeing a few more pics of the space too . IMO the first thing I would do is change those blinds to solar shades so you can have a full view out that window , have daytime privacy and heat and UV control in which case if night time privacy is an issue then the drapes .How much book shelf do you need ? Waht are going to put in them ? Is this a space you do Zooms from ? I do see the need for a much larger desk for sure not sure why 3 monitors but that really does not matter.We do need pics of the whole room posted here in comments DO NOT start another post.

In any event - for sure a longer desk for those 3 monitors.

Your inspiration pictures are great! Here are some others in a similar vein.

California Scandi-Modern · More Info

In case you want to make use of a corner:

Winter Park Renovation · More Info

Desk perpendicular to window though you're going to have all the wiring showing with this layout.

Home Office painted with C2 Paint · More Info

Is the room a potential bedroom?

if so, I would not do a built in. A nice desk is easier to remove/relocate.