Gantt Cloud uses standard JIRA links to render dependencies between issues. By default all “Blocks/Blocked by” links are processed by the plugin and visualised on gantt chart in appropriate way. Any other link type can be chosen for that purpose under "JIRA Intergration" tab in add-on's Settings dialog. In example below, Issues EP-3 and EP-4 are blocked by EP-2 and at the same time EP-3 sub-task blocks the EP-30 Epic. Rendered dependency chain for these issues would look like this:
Issue links can be edited directly from the Add-on via Issue dialog (opened when issue is clicked). Read more about editing issue links
It is possible in JIRA to make an Issue dependent on another from different project, for example, by creating "blocked by" link between them. As Gantt Cloud is now grouping issues by projects, it is not currently possible to render such dependencies on the Gantt chart. To better understand this limitation, please see an example below: Consider Issue 1 from Project A being blocked by Issue 2 from Project B, therefore Issue 1 should be rendered below and further to the right. But, Project A is the first on the left header and so are all it's issues. It could be possible to switch those two projects in that simple case (Project B could go first) but what if there are more such dependencies (e.g. A-B-A-B)? In other words, to make a proper Gantt chart the issues needs to be reordered properly and it can be done only for the issues in the same group (project in that case).
As a solution for this problem we are currently considering adding different grouping strategies (components, sprints etc) or even turning off the grouping at all. There isn't solid plans or dates yet, however.