Rather than trying to deal with tag synonyms on an ad hoc basis, I suggest a more structured approach.
- Identify a relevant area from which questions will be drawn.
- Use a discussion such has occured here to identify "all possible" tags.
- Arrange those possibilities in a logical hierarchy of specificity.
- Nominate the appropriate tag for best use on each branch.
- Make all terms below the selection synonyms.
In the case of funerary recognition, the heierarchy might look like this:
So if Grave marker is chosen to become grave-marker, then all the terms immediately to its right become synonyms. But plaque would be permitted to refer separately to the naming of cremated remains (for example).
If that decision seems "wrong" then the fault lies in the hierarchy and it should be rearranged to describe the desired logic for the whole area of memorialising ancestors; rather than just adding or subtracting individual tags.
(Note that I am NOT proposing separate tags for all those descriptions of symbols. It just so happens that the mind-mapping program allocated a style that resembles tags.)