Steps to reproduce:

1. Create Zabbix HTTP agent host item with:
   • update interval: 0
   • custom flexible interval: {$ORG.APPNAME.HTTP.INTERVAL} = 600s
   • custom flexible period: 1-5,09:00-17:00
2. After item updated, check state/error

Result:
item not supported with the error: Invalid scheduling interval "{$ORG.APPNAME.HTTP.INTERVAL}/1-5,09:00-17:00"

Expected:
Working as it worked in Zabbix v5.0 which we upgraded from (5.0.2/3 -> 5.0.42 -> 7.0.2), and as documented:

• v5.0: 2 User macros supported by location (zabbix.com)
• v7.0: 2 User macros supported by location (zabbix.com)

If macro value (in this case 600s) set on the item directly, it works.