I recently worked on an issue where the customer was interested in changing the position and size of the ITS widow that opened as a result of a launched transaction. It can be done, but the changes would be considered as modification to SAP standard code.
You can follow the steps below to change the standard coding in Java Script to control the position/size of the ITS window.
1. Execute transaction SE80
2. from the dropdown select BSP
3. enter UICMP_LTX for the BSP name and hit enter
4. Expand Pages with Flow Logic
5. double click on LaunchTransactionAdmin.js
6. scroll down to line 97 you will see
ltx_window = window.open(url, ltx_window_name, "resizable=yes");
7. and again at line 113
ltx_window = window.open(url, ltx_window_name, "resizable=yes")
8. Here is where you can modify JS method window.open to change the size
and position of the ITS window.
You can also do a search on window.open in Google and take a look at some of the examples that might assist you with the coding.