Summary
VOSviewer alternative tool
Using the VOSviewer tool for visualising the relationship between keywords used for the selected journals can be quite complicated.
After a research I came across a simple, multi-platform free tool called Gephi
It only requires a simple CSV textual file with a comma-separated list of keywords used for each article (single line for each article) to visualise the keywords relationships and identify the primary keywords, secondary and so on and the transition identified from each previous keyword to the next one.
You can also refine and omit single occurence of keywords to make the visualtisation clearer.
It is also worth noting that the order of keywords for each journal matters for the visualisation output clarity, therfore you might want to sort the list of keywords in the CSV file before using it as the input of the tool.
My keywords visualisation for all 12 selected journals can be seen below:
