Option to add additional boxes for studies excluded/included (in narrative synthesis) after quality appraisal and studies excluded/included in quantiative synthesis

[befriendabacterium]

Is your feature request related to a problem? Please describe.
Not able to easily add boxes in Inclusion section for studies excluded/included (in narrative synthesis) after quality appraisal and studies excluded/included in quantiative synthesis (as in ROSES; see image).
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Describe the solution you'd like
Add this feature and options to turn qual appraisal/narrative/quant synth boxes on/off.

Describe alternatives you've considered
Had a look at implementing a few changes/additions I wanted myself but DiagrammeR doesn't allow you to easily edit an object once it's created from my experience (unlike ggplot's + feature for example). I also briefly tried editing your source code but got some weird errors with hidden functions that appear to be in the PRISMA2020 package but not immediately accessible to users (e.g. 'PRISMA_get_height_'):

Error in PRISMA_get_height_(stringr::str_count(other_identified_label,  : 
  could not find function "PRISMA_get_height_"
 > PRISMA2020::PRISMA_get_height_()
Error: 'PRISMA_get_height_' is not an exported object from 'namespace:PRISMA2020' 

Additional context
See discussion with @nealhaddaway on his ROSES package here: nealhaddaway/ROSES_flowchart#2)