Archive Investment Transactions
For about a year now, a new function has been available in Quicken, Archive Transactions. It will split your investment account register into two parts, leaving only those securities transactions where you currently hold >0 shares in the active register. The rest is moved to a new Archive register within the current data file.
Having less transactions in your active register might improve performance.
Please read and follow instructions here: https://www.quicken.com/support/how-archive-investment-transactions