Mongodb: how to create multiple indexes on same field?
Sadly, a restriction of MongoDB:

Restrictions
In MongoDB, you cannot create multiple versions of an index that
differ only in the options. As such, you cannot create multiple
partial indexes that differ only by the filter expression.

Right now, you can only do this:
db.test.createIndex({field1:1}, {partialFilterExpression:{field2:{$gt:10,$lte:10}}})

Or use composite indexes with a placeholder field:
db.test.createIndex({field1:1, never_use_this_field1: 1}, {partialFilterExpression:{field2:{$gt:10}}})
db.test.createIndex({field1:1, never_use_this_field2: 1}, {partialFilterExpression:{field2:{$lte:10}}}