Subtask support depends on the tool you are using, while some tools support infinite levels of subtasks (e.g. Wrike) other doesn't support subtasks at all (e.g. Github).
While Asana supports subtasks, Unito does not yet sync them. Yell at us if you must have them.
Github does not support subtasks. Subtasks will therefore not be synced into Github, but will not be deleted in the origin tool.
JIRA supports one-level deep subtasks. They are synced with other tools supporting one-level deep subtasks (e.g. Asana)* and tools that support infinite-level deep subtasks (e.g. Wrike).
*Asana-JIRA subtask-syncing will be available soon. It's a priority and we're working on it! On the other hand, JIRA-Wrike substask-syncing is already available.
Wrike supports subtasks of subtasks (infinite levels); whereas other tools can only have them one level deep (you can only have subtasks under a task, but not under another subtask). The hierarchy of subtasks within Wrike, when replicated in a one-level deep subtask, will be flattened out. What this means, is that all subtasks of subtasks in Wrike will become subtasks (all on the same one-level depth) of the main task within the other tool. Rest assured though, the subtask hierarchy inside Wrike will remain unaffected.
Here is an example of subtask hierarchy in Wrike:
Once synced, this is how it will appear in JIRA for example:
Wrike supports putting a subtask under multiple parent tasks. When replicated onto another tool supporting one-level deep subtasks, the subtask will be put under the highest ancestor task that is also part of the folder being synced. If the Wrike subtask doesn't have any parent/ancestor in the current project, the subtask will be replicated as a regular issue on the other tool.
Advanced Operations: Changing the Subtask's Parent,
Converting a Subtask to a Task & Vice Versa
Sometimes you need to move a subtask to another parent, demote a task to subtask level, or promote a subtask to a full-blown task. These advanced operations are possible in both Wrike and JIRA.
Any such change on the JIRA side will be carried over to the Wrike side. However, due to limitations of the JIRA API, if these operations are applied from Wrike, the synchronization process will not apply the change automatically on JIRA.