A single SLA goal for linked issues -- is this possible?

[Kalin U]

I am faced with the following problem (Jira Service Management Cloud): I have a ticket (shared with the customer) and a sub-task (internal, visible to the service desk team). I would like to have the the same remaining time for the sub-task as the parent ticket when it comes to the SLA metric "Time to resolution".

Here are more details:

1. a customer raises a ticket in the portal and it is fetched by a support agent (Level 1) from the queue
2. the L1 agent needs assistance from an IT specialist and thus escalates (transitions) the ticket to a Level 2 agent; the ticket assignee is still the L1 agent
3. the escalation transition creates a sub-task in the same service desk project and is assigned to the L2 agent;
4. the SLA timer for "Time to resolution" is ticking for the L1 ticket; the customer sees that their ticket is "Work in progress";
5. the L2 sub-task needs to have an SLA goal equal to the remaining SLA goal of the L1 ticket (e.g. if there are 1.5h out of 2h for the resolution of the L1 ticket, the sub-task should start with 1.5h as "Time to resolution").

I only found Same SLA Parent/Child ticket using JIRA SD and JIR... (atlassian.com), but the suggestion doesn't fully cover my case. Do you have any other ideas or suggestions?