Here we go - Found a workaround solution by creating 'DUPLICATE' sheets
I noticed that the Ext arranges the sheets based on 'Sheet created Date and Time'.
Hence, the ideal solution would be; Once you are done with all your development activity
Step1: Arrange the sheets in required order ----> in the sheets TAB on the top right corner
Note - If you have multiple sheets try naming them prefixing with Numbers hierarchically.
Ex: 1.Sheet1 , 2.Sheet2 , 3. Sheet3, 3.1. Sheet4, 3.2. Sheet5....................4. Sheet7
Step2: Create the duplicate sheets for all the sheets in the same order
It look something like this;
1. Sheet(1) , 2.Sheet(2) ........................
Step3: Delete the original sheet and retain the sheets with new name '(#)'
You can 'EDIT' the sheet names with original names by removing (#).
The sheet name will be ordered accordingly in the 'My Tabs' Ext as well.
It worked very well for me