How to provide formula in action item of Guided Decision Table?

Issue

There is a scenario as shown in the following screenshot:

The parsed DRL looks like this:

pdf.setCardRenderTextOut("$" + pdf.getAmount());

But when trying to achieve the same in Guided Decision Table in BRMS's business-central it seems not possible to set any formula. It is by default parsing the formula as STRING LITERAL:

Which results in following DRL being generated:

pdf.setCardRenderTextOut("$ + pdf.getAmount()" );

How to provide an actual formula in the action item instead of String?