I am one of those many who have been requesting this feature for years.
When it finally showed up, I couldn't believe how difficult it was to implement. I have studied the instructions/tutorial/examples and still find it difficult to use.
The explicit feature seems to be quite powerful, and capable of doing much more than what most people have asked for. It's usage is correspondingly complex.
So, what I would like to see in a future version is not better/clearer documentation or any other kind of improved help, but rather to see it scrapped and start again from scratch.
It should be something as simple as this, and tied to the in-line evaluation feature:
"When you want in-line evaluation, instead of pressing "=" after the variable definition, press "ctrl-=". This will show the value substitutions, followed by the final result.
Of course for some value definitions, which could be complex, this could result in a large complicated expression of substituted values. The "explicit" feature offers the user some control on which variables are explicit. But most of the time this is not the case, and users don't need or want this type of custom control--they simply want ALL of the variables to be explicit.
That kind of simple algebra hits the wall.
Real pojects are already taken into account,
since at least Mathcad 8 Pro.