@Zvonimir Stanecic Thanks for the kind words.

Although the process is somewhat convoluted, I've figured out how to fill in the target strings containing plural forms using #transifex:

• Use ctrl+up and ctrl+down to navigate to previous / next string.
• When you navigate to a string with plural forms, the other quantity is selected first.
• You can type your translation or you can press ctrl+g to fill the source string for editing in place or you can press ctrl+h to fill in machine translation.
• When you wish to select different plural quantity for translating use the screen reader features to move the focus outside the text area, for example to the source string or to the list of quantities above the text area, then press the up arrow key and then press the tab key to focus the text area again.
• The fact which quantity is selected is not communicated to screen readers so you need to make extra care. Pay attention to the list of quantities defined for the target language. When translating from english to slovak source language (english) has two quantities configured, one and others, the target language (slovak) has four quantities configured, one, few, many and others. When navigating this way I am moving in a reverse direction from others, through many and few down to one.

I Hope this might also help someone else.