Regarding the ability to change the limits.
As per the technical article .......
Version 13.2, 13.3, 14.1
Limit on Portfolio Investments
Portfolio Management (PFM) is limited by design for performance reasons to only include up to 250 investments and 25 roles. This is documented in the Portfolio scenarios documentation guide. This is a fixed amount and is not configurable.
SaaS / On Demand Customers - this limit must remain in force.
For both On Premise and SaaS, Our recommendation is to upgrade to v14.2 or v14.3 which is soon to be released