"How to add custom excel templates that appear in the drop-down lists of D365 Finance GL journals" and "How to setup the correct dimension structure for Excel templates in D365 Finance"
Custom Templates
Adding your own custom templates to D365 Finance is tricky as it does not allow to add multiple different templates that apply to the same journal type. These instruction help you add an extra template in addition to the standard one.
New custom templates can be uploaded from Common>Office Integrations>Document templates
First thing to know is that to be able to see a custom template in addition to the default types, the file name of the template has to be exactly the same as on the default one. Also the name of the report has to be exactly the same and only the template display name can be different.
Because of this requirement (that seems like a D365 bug) and so that you do not override the default templates if you need to use them for other GL journal entries, you have to make the report appear slightly different by either selecting a language/country/company defined setting.
If all of the above has been done correctly, you should be able to see the custom template in addition to the default ones when using the "open lines in Excel" on the GL journal form.
Dimension structure for Excel templates in D365 Finance
The Dynamics 365 Finance Excel Add-in does not understand the Account Structure setups per Account that you have set up in D365. For that reason, the dimension order has to be defined in the D365 Dimension integration setups. (General ledger - Charts of accounts - Dimensions - Financial dimension configuration for integrating applications)
For Ledger type excel lines, which the Accrual transactions are, use the Ledger dimensions integration setup and select all the dimensions needed in the correct order.
