Yes I do think we need such a tag (homing), homing is a specific action that should be identified as such. I've added the tag to a specific question on homing and will go through the questions to re-tag other questions. Also, the tag x-axis is also very beneficiary.
Having 2 change tags seem a bit over-redundant.
Tags I'd like to see for such a question are: filament and pause. The question is about pausing the machine (in which he changes the filament).
In terms of searching there may be a need for a tag change-filament, or at least a tag change or maybe better like @Greenonline suggests: swap or changeover?