Greetings,
!very hard to edit math strings without explicit "editor manual"
I will admit, there is a little bit of a learning curve (especially if you migrated from Mathcad) when it comes to using the keyboard to navigate an equation. For me, moment of epiphany happened when I realized the cursor movement wasn't with regards to onscreen display/graphics, but rather the inline math statement being considered.
3.) Consider the merits of a command line (similar to the debug window) where, upon the selection of a math region, the inline text of the math statement/expression (e.g., "line(j:-1,for(і:1,і<10,і:і+1,j:і+j),j,3,1)" ) will be displayed; that you may edit directly within the command line interface (or at least display the current 'cursor' location within the inline expression for the given onscreen cursor location of a math region.
May this be of Good Help,
⚜ Kenny Lemens, P.E. ᵂᴵ
"No matter where you go, there you are." -Buckaroo BanzaiHotkeys: https://en.smath.com/forum/resource.ashx?a=45771&b=2