One thing that I am glad about, is that at least, I now know how-to.
On the other side, I had not realized that it could slow down the
process, as a matter of fact, I thought it was the opposite.

As for defined names (or created names), I use them a lot!
I define names for ranges of cells or create names for single cells.

I went to look at the link that you gave to me, in case I would have
missed something important (I am new to vba  but I've been using Excel
for very long).
But no.
Defining or creating a name sometimes is a must, always makes the
formula easier to understand.
And most of all, if you move the cells (or the range) around in your
workbook, you can still refer to them wherever they are, because the
names move with them, if I express my-self well.

But it does not define the formula it-self to be used somewhere else.

Sure I can name a cell "ThisCell", and somewhere else use the
formula "=ThisCell", but it bring me the value of the content
of "ThisCell", and does not rewrite the formula that is in "ThisCell".

I guess that if I wanted to create functions  to replace  my very long
formulas, it was mostly... for esthetic reasons :-)

But you have proven me clearly that I was re-writing the Worksheet
function, so now I will use it very sparingly, only in a very long
sub.