Hi Marcos,
I do not think, that this is the correct solution of the usability 
problem. Each buttons in the right column can be combined with each one 
on the left side.
For me the solution is still (see issue) to make a new icon, where the 
sigma is replaced with a placeholder sign.
Other equation editors (Microsoft, MathType) do not provide two parts 
the user has to combine, but collections, where the parts are already 
combined. So another solution can by to divide the current group in the 
upper part into three groups where each group has all combined formulas 
of its kind. That solution would need a lot of new icons.
Kind regards
Regina
Marcos Souza (via Code Review) schrieb:
Hi,
I have submitted a patch for review:
     https://gerrit.libreoffice.org/4067
To pull it, you can do:
     git pull ssh://gerrit.libreoffice.org:29418/core refs/changes/67/4067/1
Fix fdo#32720: limit buttons doesn't add the sum sign
Change-Id: I9086707f14335ea26bb94c36ee0f87e770c9418b
---
M starmath/source/commands.src
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/starmath/source/commands.src b/starmath/source/commands.src
index e6a002f..26ece56 100644
--- a/starmath/source/commands.src
+++ b/starmath/source/commands.src
@@ -149,9 +149,9 @@
  String RID_LLLINT_FROMX     { Text = "lllint from{<?>} <?> " ; };
  String RID_LLLINT_TOX       { Text = "lllint to{<?>} <?> " ; };
  String RID_LLLINT_FROMTOX   { Text = "lllint from{<?>} to{<?>} <?> " ; };
-String RID_FROMX            { Text = "from{<?>} <?> " ; };
-String RID_TOX              { Text = "to{<?>} <?> " ; };
-String RID_FROMXTOY         { Text = "from{<?>} to{<?>} <?> " ; };
+String RID_FROMX            { Text = "sum from{<?>} <?> " ; };
+String RID_TOX              { Text = "sum to{<?>} <?> " ; };
+String RID_FROMXTOY         { Text = "sum from{<?>} to{<?>} <?> " ; };
  String RID_ACUTEX           { Text = "acute <?> " ; };
  String RID_BARX             { Text = "bar <?> " ; };
  String RID_BREVEX           { Text = "breve <?> " ; };
Context
   
 
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