First, you need to install the Toolbox plugin, then you can add the JavaScriptToBubble element.

Be sure to give it a unique suffix (with no spaces) - that’s what you’ll use to ‘call’ it from within your other RE.

And check the ‘Trigger Event’ box.

Once the element is added, you’l be able to create a workflow based on that JavaScript to Bubble element being triggered:

Here you can add whatever actions you need (i.e. showing the popup).

Then, in your other RE, when you want to call that JavaScript To Bubble element (and therefor trigger whatever actions are in the trigger workflow), just use a Run Javascript action with the following code:

bubble_fn_openPopup(); (openPopup being the unique suffix you gave the JavaScriptToBubble element - which can be anything you like).

Then, when you run that action from your RE, the javascript will ‘call’ the Javascript to Bubble element on your page, which will trigger the workflow to open the popup (or whatever your workflow does).