To my knowledge,
an .asc converted to .asy for use in another .asc
will consider pins but not params.
Similar to the Attribute Editor and Pins Editor,
could a Parameters Editor be added,
which allows PARAMeters to be added to the symbol,
optionally given a default value, and
optionally given a default visibility/text placement.

When the symbol is placed for use in a parent .asc,
its right click menu would include the Parameters table.
The default values and visibility would be editable.
These values would be overwritten by code in the PARAM/SpiceLine input box.


This allows symbol creators to specify mask PARAMs
which are most salient or most likely to be changed,
for ease of use and readability in the table,
as well as readability in the schematic since
visible parameters could be moved around on an individual basis
rather than shown all in one line line in PARAM/SpiceLine.
Additionally, PARAM/SpiceLine would still exist to overwrite
any PARAMs not in the table (or PARAMs in the table if specified in both places).