"I was going to do a 'split' with the expenses".
"I have a category called '{rental property name} Expenses' but it won't total all of the expenses in groups".
Assuming I understand you correctly, why would you expect one category to provide sub totals for - what clearly seem to be - multiple different categories? Create separate categories for each expense type you want to track (*).
For the rent income transaction: have one split line for the gross rent amount, followed by a separate split line for each expense you want to track
- expenses paid by the property management company - (management fee, plumbing, gardening, etc.). The net amount of that split transaction will be the amount you deposit in your checking account. [I'm assuming your property management company notifies you of the specifics of the deductions they take from your gross rent.]
If you pay some of the expenses directly (the management company does not pay them, then deduct them from the rent they send you), then record those expenses separately from the rent deposit split transaction.
[ (*) You can certainly have a Parent category called something like "Rental Property Expenses", with Child categories such as "Gardening", "Management Fee", "Plumbing", etc.. But you don't need a unique parent expense category with multiple child categories for every property - use the same gardening category ("Rental Property Expenses: Gardening"), for example, for every property ... but Tag each transaction with the appropriate Property Tag.]