Enable search GL Accounts by Account Number.

QuickBooks Desktop

1. Select Edit > Preferences.
2. In the Accounting section, Company Preferences > Check Use account numbers.
   
3. In Acctivate, run a sync
4. When editing the GL Account in Acctivate, open the search window change Find Account Where to Account Number.
   
   

QuickBooks Online

1.  Select the Settings icon > Account and Settings.

2. Select Advanced.

3. Enable "Enable Account Numbers":