Timeline can select hidden pieces

[leozide]

Selecting a hidden part in the timeline allows the user to edit the invisible part. It even shows the widgets for it.

[nathaneltitane]

Is this actually a bug? If anything, could we maybe introduce an option for the user to enable selection/deselection of all parts while even hidden?

I for one often hide pieces that are on the outer layers of a model to better see and position certain parts when framework view makes this to complex to distinguish: I will then select all (Ctrl+A) and then deselect, or select inverse to then reposition things and hope for the hidden ones to follow as well (which they currently do not somehow?)

[nathaneltitane]

ref latest bug reports - timeline should allow full selection of all items, invisible or not to permit cross file copy/cut/paste as disabling this behavior (unless a user toggle is made available) makes the management of steps, parts and their editing a nightmare)

Rationale would be to add/enable a 'lock' that would disable part selection/editing and that should be separate from the 'hide' feature - again, a part that is hidden is invisible, not 'uneditable'

For convenience, an option could be made to `hide+lock' that could be set at the user's convenience depending on editing workflow and model complexity