When I used Mathematica in graduate school, I would ubiquitously specialize
a variable and then later "un"specialize it. Specifically, for example, I would write

v:= x^3;

Then, later, when I wanted the symbol "v" to be left symbolically, I would redefine it
with nothing following the definition

v:=;

I forgot the exact syntax, but it was something like this.
But, I cannot find this feature in Maple. Yet I badly need it.
Currently, for me to recover the use of a symbolic variable name like 'v',
I have to CLOSE DOWN MY DOCUMENT and REOPEN IT!

Secondly, in Mathematica, I easily evaluated the "independent" variable to a value
and then could get the value for the dependent variable. The syntax was something like:

e.g. v:=x^3;
x/.->3;
v;

would return 27. Actually, in Mathematica, I believe the semicolons SUPPRESSED the output,
the reverse with Maple.

Finally, how DO I suppress output in Maple?

I hope (demand, since I paid for Maple out of my own pocket) that Maple can do
everything Mathematica can do.
Thank you for your help.