A couple of the features you asked for were recently added, in v14 I think:
To get "in-line evaluation" you just press "=" at the end of your definition "F := m.a" and you will see "F := m.z = 6"
However, there have been some bugs reported (and I have also observed) that the evaluation part "= 6" does not recalculate properly, and can therefore show incorrect results. This is too bad. I wanted this feature also, very badly, and was thrilled when they added it, but they blew it. This bug is so bad, I do not use the feature anymore.
Using "symbolic evaluation with keyword" you can get F:= m.a --> 2.3 = 6
However, the procedure needed to get it to look just like this is so contorted, that I also do not use this.
It's too bad that PTC can't implement simple features like this in a bug-free way.