The goal is to select and cut the second column and then paste it to the left of the first column, which these next 3 commands do perfectly:
cut selection
select insertion point before first character of second line
paste column characters
BBEdit rectangular/columnar text selection
The other method is to do this row by row, but this is much slower than a rectangular selection followed by a Cut and a Paste Column.
Input example:
"Key":"A0Qk9DVpUkGulGpHxr+JlW4=","PageNumber":1
"Key":"AEcL8VGZFEUCeSx5vvCxto0=","PageNumber":2
"Key":"ABVH60Q2pc+AePwQNAdmMdQ=","PageNumber":3
"Key":"APqXJ0lwaCrLtVJlbBnc6mI=","PageNumber":4
"Key":"ABcrwNYHkx+qPTbzuUHlYEI=","PageNumber":5
"Key":"AJZ+S/Y9PJ2o42lqMnPlAN4=","PageNumber":6
"Key":"AAWHU3+jHUoMqLsJ4s4zQMs=","PageNumber":7
"Key":"ANG5KxVCEToVhf9gDKcM93E=","PageNumber":8
"Key":"AL3A2YbsAuQvUPWZDHTlssE=","PageNumber":9
"Key":"AH8buWygY/hZ9VHnoyMuIEs=","PageNumber":10
"Key":"AHZNQ3E90ySyEiwQZWBoEuc=","PageNumber":11
"Key":"AJHkHd/ZVdUZIFo4FcYwXnM=","PageNumber":12
"Key":"AEbWD9Hsrl9Uig+p0am6Rj4=","PageNumber":13
"Key":"APE5vIEkT0Y3/2Tv/ElfJiA=","PageNumber":14
"Key":"ALG40gmAwr/id3DJnczzuSE=","PageNumber":15
"Key":"ABeop321v++Ki3T8uc7ouuM=","PageNumber":16
"Key":"ABgh96CHbwrASAVqo/Nqtf4=","PageNumber":17
"Key":"AF6+J/oF4We4Cjumo+b34eY=","PageNumber":18
"Key":"A0BLp58WhLAlt+ArrbJ52vQ=","PageNumber":19
"Key":"AIDBCaRs3y9nkZJMwMx8HTg=","PageNumber":20
The output should follow this form:
"PageNumber":1,"Key":"AOQk9DVpUkGulGpHxr+J1W4="
"PageNumber":2,"Key":"AEcL8VGZFEUCeSx5vvCxto0="
"PageNumber":3,"Key":"ABVH60Q2pc+AePwQNAdmMdQ="