categories: checkboxes only available for leaf elements?

[bakhshir]

Currently there are no checkboxes for the parent elements, if a node/category has a child element; only leaves have checkboxes.
For example,

in this case, I might know that a project used SURF infra but not aware which service was used. I still would like to check the box "SURF...".

This leads to another UX issue: for the trees that have branches with unequal depth, the missing checkboxes put different spacing, and even different font styles.

[bakhshir]

Another suggestion for UX improvements is to introduce +- to expand and contract some (sub)categories to make it easy to ready. Relevant to the issue #1341

[bakhshir]

Just to note that without having checkboxes enabled at the parental elements from the start, forces me to come up with the "creative" ideas like this: https://research-software-directory.org/projects/error-detection-and-error-localization (subcategory for "catch-all" clause).

Also, in some projects, we have detailed information about infrastructure like this one: https://research-software-directory.org/projects/exaflow But for some projects, we do not have this detailed information anymore, and need flexibility to be able to check higher level (sub)categories.