My dad owns ~450 stocks. I’d like to help him trim it down to a more manageable size. Any suggestions?

My dad has developed dementia, so my mom and I have been trying to help him with his investments.

We recently discovered a portfolio containing ~450 individual stocks.

I find this to be unmanageable (especially for someone with dementia).

Any tips on responsibly trimming this portfolio down to 20-50 holdings?