Can you give us more information on exactly what you are trying to do and why? I can't deduce it from your question.

I need a way to store 8000 char string into SQL and link it to the current DocumentID on the LF client.

This button should only appear when the current template in the LF client is Invoices'

This string is used to store GL coding string to integrate to the ERP. They do not want to use 2 text fields.

You can find sample code for setting up custom toolbar buttons here: https://support.laserfiche.com/GetFileRepositoryEntry.aspx?id=2878&mode=download.Check out the "Investigation Management" sample program. Basically your custom button will use the %(DocumentID) command line token, which will be replaced with the IDs of the currently selected entries. There is no way to disable a custom button based on the template, we will look into adding that to a future version.

it appears I do not have access to that file.

can you attach it in here pls

I also am blocked from that download.

The basic idea that they are promoting is that you build a custom console application that takes command arguments or uses CAT to get the entry information.  Then you use RA to check the assigned template.  If the proper template is assigned, have your custom application proceed with the updates.

Your custom toolbar button calls your custom console application and you get the functionality that you are looking for.