I want to fetch the task Id which will be present in the sub process.

Query process analytics can help,
forum.appian.com/.../System_Functions.html

Hi Ravir,
Create a process report from the Appian designer, select report type as "Task", select context type as" Tasks by process model".
Configure the report with the main process model and select "Yes" for Include data from sub-processes. Also in the report configure a column of the report as checked for "Link to more information" - > "Link to" as Task Details - > "Task" as tp!id.
Then using the Query process analytics method as mentioned in the link above, you can get the data subset that will contain all the required data which can be manipulated based on the requirement.

Thanks both of you!!

@ravir I would like to comment as follows, on what other practitioners has mentioned so far:

Re function:
Usage of the function entirely depends on the version. Usage of a!queryProcessAnalytics() is permitted ONLY if you are on or above Appian v7.8. Else fn!getportalreportdatasubset() (A plugin that was deprecated after the introduction of a!queryProcessAnalytics() in Appian v7.8) is an option for you.

Re approach:
You might take a look at the approach as specified above but prior to opting for it, I would like to suggest to have a look at the following:

1. You will get the task information from the sub-process (which you are aiming at) and also the main process and other sub-processes in the same. So this means that you will end up in having task information from 3 different sources, that is, the main process on which you constructed the report, the sub-process which you already have and aiming at, and the other sub-processes in the same.
So, think of applying a filter based on the sub-process from which you want the task. In simple English, the query should be like 'Get the tasks from main process which belongs to a particular sub process.'

2. In the main process model, did you configure the sub-process node (i.e. the node which is MNIed) with the option 'Allow data from this sub-process to be included in reports on the parent process model.'? If not, as per my knowledge, this approach doesn't work and you need to tweak it.

3. Did you select 'Delete previously completed/cancelled instances' on MNI'ed node? If so, as per my knowledge, this approach doesn't work definitely because the parent-child relationship will be decoupled upon selecting 'Delete previously completed/cancelled instances' and thereby they won't appear in the report.

Thanks sikhivahans,
Yes I am using Appian 7.8 so I am fetching portal report on my sail form using
fn!getportalreportdatasubset and it is working.

Glad to hear that, If you are on Appian 7.8, please switch over to the usage of a!queryProcessAnalytics. Please do bear in mind that fn!getportalreportdatasubset() troubles you in querying huge datasets.

Hi sikhivahans,
I tried with the a!queryProcessAnalytics however I am not getting any value, I tried with the approach provided in the SAIL Recipes, It showing me "No items available".

Please find the below image for reference.

It means that there could be some or the other problem with the implementation. If you can discuss implementation (category of report, type of user (that is basic or system administrator) under whom the report is being executed, filters if any etc) in an elaborative manner, practitioners here could definitely get you on the right track. Further I would like to suggest you to strictly stick with the usage of queryProcessAnalytics as the usage of getportalreportdatasubset isn't appreciated by Appian since 7.8.

Its Task--->Task by Process Model, user is system administrator, and also need to filter the data based on logged in user