The following shiurim say that moving outside requires a new bracha rishona even if you come back inside to eat.
According to New Beracha after Moving Between Rooms implies that outdoors does require a new bracha
The best method to avoid doubts is by having in mind at the time of
the beracha that you will be moving from room to room, and in this
case one does not get into doubts, and it is permitted to move from
room to room (but not outdoors) without making a new beracha
There is a series of shiurim on Jewish Pathways that deals with this issue says that walking outside requires a new bracha as long as you are not eating with other people and they remain.
Mishnah Berurah 178:2
In determining when a change of place effects a shinuy makom, the
halacha takes three factors into account:
1) What type of location change did you make: a minor change (e.g.
from room to room), or a major change (completely out of the house)?
2) What type of food were you eating?
3) Were you eating alone, or with others who remained in the
Not every change of place signifies the end of an eating session. Only
a major change, i.e. one that you would not normally make in the
middle of eating, terminates your bracha. Let's explore the
Leaving the house
Orach Chaim 178:1; Rema – Orach Chaim 178:2
Mishnah Berurah 178:39
Walking outside of your house implies that you have stopped this
eating session, and is therefore considered a shinuy makom. This is
true whether you go out to the street, or even simply walk out to your
own backyard. As soon as you leave the building where you started
eating, you've made a shinuy makom and a new bracha is necessary if
you want to continue eating.1
This is true whether you want to continue eating outside, or even if
you immediately come back inside to continue eating there. The mere
act of leaving the house ends your original eating session, and
terminates the original bracha along with it.
The reverse is true as well. If you began eating outside, and then
walk into your house (or any other building), a new bracha is
necessary if you want to continue eating.2
In the summary
Rabbi Y.S. Elyashiv, cited in Halachos of Brochos, pg. 146, footnote 26.5; V’Zot HaBracha, pg. 61, citing V’Tein Bracha 146
Mike is eating alone in a crowded school cafeteria. He leaves the
building for a minute to make a phone call. That constitutes a shinuy
makom – even though when he returns there are still hundreds of other
people eating in the same place – since Mike was not “eating
together” with those people.