Dear Muhammad,
The method that you are currently using and the method you wished so much to have leads to one common thing - manual activities.
There is another possibility to fulfill your requirement. Suppose I have alternatives BOM1, BOM2 and BOM3 with Alternative number 1, 2 and 3 respectively. Now you wanted to have BOM3 as default and to be considered in MRP, costing (application areas), but since you have maintained the alternatives in a wrong sequence, MRP is picking up BOM1 only.
Here is the solution that you can use in your case.
1. In OS30, make sure you have 'AltSel' indicator active according to the applications (PP01, PC01).
double-click on the application and make the 'Alt. det. mult. BOM selected.
2. In the material master MRP4 view, maintain selection method = '1': selection by explosion date.
3. In OS32 configuration, you can maintain what are the alternatives to be selected date-wise.
In OS32, thus I will maintain alternative 3 (BOM3) for this material, plant, BOM usage combination.
Please test this extensively before implementation.
Best Regards,
Rajen