I am hoping to implement the following, if possible.
Custom Fields to be created:
A - Test
B - Test 1
C- Test 2
Only A & B are compulsory when creating a ticket
But when a.1 and b.3. is selected then A, B and C are compulsory
Not too sure how this would be implemented but I suspect a specific code for this, but that is a bit beyond my capability.
Taking you at your word that you want field C to be required when a.1 is selected and at the same time b.3 is selected, you could try a script like this:
def fieldA = getFieldByName('A - Test') //this is the label for the field A
def fieldB = getFieldByName('B - Test 1')
def fieldC = getFieldByName('C - Test 2')
def fieldAValuesThatTriggerFieldCRequired = ['a.1. E'] //this has to be the label of the option
def fieldBValuesThatTriggerFieldCRequired = [ 'b.3. L'] //you could add additionoal values here in coma separated list
def valueA = fieldA.value
def valueB = fieldB.value
def fieldCIsRequired = valueA in fieldAValuesThatTriggerFieldCRequired && valueB in fieldBValuesThatTriggerFieldCRequired
You would put this code in the behaviours section of script runner. Create a new configuration that maps to your project. Then edit the behaviour configuration and add field A and Field b.
For each of those 2 fields, add a server-side script and put the script above in each of those server-side scripts. These server-side scripts run each time values change in each of those fields so that the fieldC can be re-evaluated each time.
To make fieds A and B required, you can do it with the behaviour toggles on each field. Or you can make this globally required in your project's field configurations.