When you create a turnout, you can use an option on the Diverted Alignment tab of the Create Turnout dialog box to merge the turnout's diverted alignment with an existing alignment.
Likewise, on the Profile tab, you can select an option to merge the diverted alignment's profile with an existing profile.
You may need to manually connect the entities of the turnout and the merged alignment and profile after the turnout is created by drawing additional alignment and profile entities. You can do this by using the alignment and profile editing commands.
For example, when you create the turnout, the entities may appear as follows in plan view, where the diverted alignment extends from the turnout on the left and the alignment it's merged with is on the upper-right:
You can use the alignment editing commands to connect the two as shown in the following example:
You can connect a turnout's diverted profile with its merged profile using a similar workflow, except you select the diverted profile in the profile view, right-click and select the Edit Profile Geometry command.
For example, when you follow the steps above, the turnout entities may appear in profile view as follows, where the diverted profile is on the left and the profile of the alignment it's merged with is on the right:
After connecting the entities with a free vertical curve, the profile appears as follows: