Hi @Gabe,
thanks for the fast answer and sorry for my quitness, I had to finish the project, before I could check your answer in detail.
First of all: There are no distinctions between different kinds of baseline grids in the documentation, at least in the german version. Thanks to your hint I did understand now, that I can combine as many different baseline grids as I want for different overlapping objects - for which purpose ever.
But IMHO the main purpose of the baseline grid is, to keep all the text lines in sync in the whole document including e.g. table rows and except specific lines, where I switch the baseline grid explicitly off (for example for picture captions).
As you can see in the screenshots I added the baseline grid and the table functions interfere with each other in a non consitent manner: The row border does not reflect the end of the line, crosses the text and ignores other paragraph details. This is getting worse, when I use more than one baseline grid. I only could get the text flow to work, when I fully switched off the grid and defined the line alignment manually - than I do not need the baseline grid at all in tables.
So, if the bevahiour is technically spoken no bug, because it perhaps works as designed, the behaviour is futile and hindering this way. Than please think about redesigning it.
Thanks, Ulderico