Adobe Illustrator lets me make my own toolbars!

They don't have the concept of separators. Grouping tools either involves making a separate toolbar for them, or stacking several tools in one button that, when pressed and held, pops the stack out so it can be dragged off as its own pseudo-toolbar.

The catch is that these pseudo-toolbars only have two options for resizing: single column or single row. They can be snapped together horizontally, but not vertically.

In fact, standard toolbars also only have two size options: single column or double column. They can't go horizontal. Worse, when switching from double to single, the column isn't merely split in half to keep both halves in order; the buttons are reordered in horizontal pairs, essentially requiring relearning the positions of every button but the first. These toolbars also only snap together horizontally.

Then there are the utility panels: one for setting text properties, one for manipulating object appearance, one for managing layers, and the like. Some can be resized freely for both height and width, some have multiple fixed size modes, and all can be reduced to tabs or even buttons. These can be stacked into little tab groups like the pseudo-toolbars, and those can also be attached vertically into columns which can be snapped together horizontally.

None of these can be pinned to the top or bottom of the window, only left and right or free-floating.

Oh, but there's also the "control bar" which can only be docked at the top or bottom of the window and, when free-floating, always takes the entire width of the screen and cannot be resized at all.

This product has been in constant development for 35 years and its UI is still baffling and inconsistent yet I persevere because (despite the existence and usability of Affinity Designer and the existence... of Inkscape) so far Illustrator is still the best tool for how I want to do things.

Computer bad. Rant done.