It might help to be familiar with how expressions are structured in the Wolfram Language. Try reading through some of the tutorials here, particularly this one about expressions as trees and then this one about extracting certain levels of these trees.
It looks like your expression has a lot of smaller repeating subexpressions. As far as I know there isn't a great way to deal with simplifying such expressions built into the language; one that would extract these repeating subexpressions, replacing their instances in the original expression with some unique variable and then annotating the whole thing with maybe an
Inactive[With] to mimic the "where x = ..." often seen in mathematical literature.
One thing you can do to approximate this feature is to enumerate all of the subexpressions that appear in your expression and see which ones appear most often, then do a simple
ReplaceAll. For example, if you have an expression like the following
assigned to a symbol called
expr, I could do the following
Level[expr, -5] // Tally // MaximalBy[Last]
to find which subexpression (subtree) with height of at least 5 occurs most often. Assigning this subexpression to
subexpr and then using
ReplaceAll you get
expr /. subexpr -> x
which is clearly a much smaller and more manageable expression.
While not a comprehensive answer, hopefully this gives you some additional avenues to explore beyond what other users have suggested.