Insert row numbers into column A, reflect correct row numbers when I add or delete rows

I want to insert row numbers into column A of a worksheet. I want the column to reflect the correct number of the row, even when I add or delete rows. The Step Value is 10 and every third cell gets numbered. This sheet is a work order and cells are deleted that aren't being used. So, if cells A4-A6 are deleted and so forth accordingly, then I want to keep the same numbering sequencing. The adjacent column B has work instructions, or sometimes says "DELETE OPERATION" if those instructions aren't required. If column B says "DELETE OPERATION" I will delete the required cells. If I do that I want the rows in column A to reflect the correct number of the row.

Example:

10 DELETE OPERATION


20 DELETE OPERATION


30 Assemble Bellows to Weld End
Weld per Drawing

40 Visually Inspect Welds


50 Air Hose Test per SWI-P-02


Formulas I have tried but do not work: =IF(TRIM(B1)<>"",COUNTA($B$1:B1)&".","") and =IF(TRIM(B1)<>"",ROW()&".","")

I found a formula that works perfect:

in A1 enter
=IF(B1<>"",10,"")

in A2 enter
=IF(B2<>"",MAX($A$1:OFFSET(A2,-1,0))+10,"")
and copy this formula down for as many rows as required. Now every time
someone enters data in column B column A shows a ID value.