In the next release of Express Generator, it will be easier to make it.
Please watch for Express Generator v2.47.

For example,
REM Generate In Sample 90%
...
--use_data_start true ^
--data_start "2021-01-01 UTC" ^
--use_data_end false ^
--data_start_percent 0 ^
--data_end_percent 90 ^
--collection_capacity 10 ^

then in REM Validated OOS 10%
.. --use_data_start true ^
--data_start "2021-01-01 UTC" ^
--use_data_end false ^
--data_start_percent 90 ^
--data_end_percent 100 ^

Will this work? Thanks
Regards,
AFR

Please see the OOS example here: https://forexsb.com/forum/topic/9278/ge … idate-oos/

I'll use the same workflow but will make a command that runs it on 8 different markets.

To make it work, I modify the OOS example to accept parameters.

Here I set a variable symbol to take the first param and a variable period to accept the second param.

set symbol=%1
set period=%2

Then I use the symbol and period params instead of hardcoding the symbol and period.
We use a variable by surrounding it with %.

node .\bin\fetch.js ^
  --fx-rates      false    ^
  --symbol        %symbol% ^
  --period        %period% ^
  --max-data-bars 20000
...
node .\bin\gen.js ^
  --symbol        %symbol% ^
  --period        %period% ^
  --max-data-bars 20000 ^

By having the symbol and the period as parameters, I can run this command from another.

oos-workflow-runner.cmd

START oos-workflow EURUSD M15
START oos-workflow GBPUSD M15
START oos-workflow USDJPY M15
START oos-workflow USDCHF M15

START oos-workflow EURUSD M30
START oos-workflow GBPUSD M30
START oos-workflow USDJPY M30
START oos-workflow USDCHF M30

Now I can start the oos-workflow-runner.cmd command and it will run 8 different oos-workflow commands in 8 separate CMD instances.

Now I have 8 sets of generated In Sample collections and validated top 10 collections with 1 click.

This is the true magic of the Express Generator