I can’t seem to get the spacing “o+10” work? Neither “o-10” etc.
Is this a known bug or am I doing something wrong?
If you use a calculation then you need to add the “=”. “o” will work “=o” will work, “=o+10” will work, “o+10” will not. Not sure why. I can’t see a reason why we need the “=” at all.
Aha, yes that works.
Yes, I agree, the “=” is redundant.
What happen if you have a glyph name like a-10? It is not very likely but still possible.
Not very likely 
a.10 is, but not a-10.
I like when things are logical, and stripping the equal would be very logical.
Georg:
Sounds logical but what would I do if I have a glyph named a-10 and I want another glyph to be 5 units tighter than a-10? That would be impossible, I guess. How would “=a-10-5” be interpreted?
It seems currently we do not have a really complete and consistent system, covering some but not all unusual cases.
Mabe it would be better to define a workaround for those case when someone uses a minus in the glyph name. For example, quotation marks to make the minus part of the glyph name:
• a-10 makes it 10 tighter than the glyph named a
• “a-10” (with quotes) makes it the same as the glyph named a-10
• “a-10”-5 makes it 5 tighter than the glyph named a-10
Nicer syntax for 99% of the cases and a solution for all possible cases.
I agree the = is redundant and I like the Tim’s recommendation.
If consistency is your main concern, then always add the equals sign, i.e. also “=n”.