This ticket adds the 'internalQueryForceClassicEngine' flag which allows users to configure the use of SBE at runtime. The flag will be set to false by default, meaning that SBE will be used wherever possible. If a user wishes to disable SBE, they can do so by setting 'internalQueryForceClassicEngine' to 'true' like so:
db.adminCommand({setParameter: 1, internalQueryForceClassicEngine: true})
Similarly, SBE can be re-enabled by setting 'internalQueryForceClassicEngine' to false:
db.adminCommand({setParameter: 1, internalQueryForceClassicEngine: false})