A file full of what's wrong with the other parent answers half the question, at best.
The question being asked is what arrangement is best for these children, not who behaved worse.
The frustrating part
A case built entirely on the other parent's failings reads as one-sided even when every complaint is true. Being right isn't enough, and it isn't even the main thing being assessed.
The other half is you: a clear, evidenced picture of who you are as a parent.
Build it by theme
The themes that tend to matter:
- Day-to-day involvement
- Continuity and stability
- Your children's wider world: family, friends and activities you support
- How you respond to what they need
- Your own co-parenting conduct, especially when it was hard
Evidence, not assertion
"I'm very involved in their education."
That's an opinion.
"I attended 11 of the last 12 parent-teacher meetings, and the school's sign-in record confirms it."
That's a fact.
Two or three examples like that per theme, each with something independent behind it, does far more than pages of general description.
Order matters
Lead with who you are. Put the concerns about the other parent after, calmly and specifically.
That ordering matters more than almost anyone expects. Start with the theme you have the most evidence for; it's usually school.
General information, not legal advice. Court process differs between countries and regions; check anything that matters to your case with a qualified lawyer where you live.
This is Chapter 10 of the workbook. Worksheet G, the positive case worksheet, takes you theme by theme, with space for two or three evidenced examples each, who could independently confirm them, and what a sceptical reader might say against them.
See the workbook & spreadsheet